John O' Groats is the northermost point in the Scottish mainland. As for the "reckless stain of cairn," I'm afraid that's a mis-translation so ignore it in future. The first word is "rickles" which means a heap, or a pile of stones, known as a cairn. Now, this is where it gets difficult and where even most Scots can't figure out what Jimmy McBeath is singing, but to understand it you must be aware of semi-archaic North East Scots. The line would be written as, "And aye the rickles of cairnies mark the hoose o' John O' Groats," but cairnies is pronounced, "c'yarnies." k-yarn-ies

The most common version mentions "Urquharts bonny glen," no mention of faires. Glen Urquhart is beside Loch Ness, in the highlands of Scotland.I hope that clears a few things up for you. :)